Threading appliance



NOV. 16, 1954 F. NELL 2,694,322

THREADING APPLIANCE Filed Oct. 20, 1 949 3 Sheets-Sheet l FREDERIC NELL98 oo Nov. 16, 1954 F. NELL THREADING APPLIANCE 3 Sheets-Sheet 2 FiledOct. 20. 1949 FREDERIC NELL Nov. 16, 1954 F. NELL 2,694,322

THREADING APPLIANCE Filed Oct. 20. 1949 3 Sheets-Sheet 3 iii! 56 5 Fig.15

' FREDERIC NELL anew-4 United States Patent THREADING APPLIANCEApplication October 20, 1949, Serial No. 122,466

6 Claims. (Cl. 80-6) This invention relates to tools or appliances forrolling screw threads and particularly to appliances for automaticmachine tools wherein a pair of spaced threading rolls are mounted in aholder and are thereby fed laterally toward a rotating work piece.

This application is a continuation in part of my previous applicationSerial No. 762,581, filed July 22, 1947, now abandoned.

It is usual, in tools of this kind to employ threading rolls which arepositively geared to rotate at the same rate of speed. The motive poweris supplied by the frictional contact of the rolls with the power-drivenwork piece. The lateral feeding of such a thread rolling device, whileuseful in avoiding an axial feed which is sometimes impossible due tothe nature of the Work, has certain inherent difficulties which are noteasily overcome. As shown in the patent to Gould, No. 2,257,234, issuedSeptember 30, 1941, the two rolls of such a device contact the workpiece initially on a plane spaced from the central plane of the rollswhich latter plane must be reached to'finish the thread. In other wordsthe rolls contact the work initially at points-which are less than 180apart on the circumference thereof. As the thread rolling operationprogresses, this angle increases until it becomes 180 at which time thenarrowest part of the opening between the rolls is reached and thethread is finished.

Therefore, the lateral relationship between the threads on the two rollsvaries as the rolling operation proceeds and provision must be made topermit such variation. A resilient connection between the two rolls,such as that shown in the patent to Afileck, No. 2,355,132, issuedAugust 8, 1944, is undesirable for the reason that failure of the rollsto assume their correct position before the start of an operation, forwhatever reason, cannot be corrected after the operation has begun. Thisis due to the fact that such correction would have to be made byindependent rotation of one roll, which is not possible. The system ofpermitting relative lateral movement between the two rolls while theyare being driven at the same rotational speed, as shown in theaforementioned patent to Gould, is preferable because any initial errorin the relative lateral positions of the rolls can be instantly overcomeafter the start of the rolling operation by the lateral movement of oneof the rolls. Such prior devices are, however, expensive and must bevery accurately manufactured to produce work pieces having accurate anduniform dimensions. Moreover, high production of threads is a necessityfor such a device, and such mechanisms, even though initiallyconstructed to a high degree of accuracy, will not long retain thataccuracy under operating conditions. These objections to the priordevices I eliminate by the use of novel compensating mechanisms whichpermit accurate adjustment Without sacrificing any of the essentialrigidity of the tool.

Devices of this same general description have been provided with taperedor frustoconical rolls for the pro-' duction of threads on tapered workpieces. In these prior tools, the tapered rolls are invariably mountedwith their axes parallel so that the larger end of the roll operatesuponthe smaller end of the work and vice versa. Since rolls and work piecerotate at the same speed, such lack of proportion between adjacentdiameters of work piece and rolls makes uniform surface speed of thecontacting surfaces impossible. Undesirable slippage thus resultsbetween the surfaces of rolls and work piece at both ends and purerolling action without slippage occurs only at the lateral mid-point ofthe rolls and work piece. I have greatly improved the efficiency andincreased the useful life of the rolls by mounting them on axes whichare inclined to each other and to the axis'of the work piece to a degreewhich will permit the larger and smaller ends of the rolls to operateupon the larger and smaller ends, respectively, of the work piece. Thusadjacent surfaces of rolls and work piece move at the same linear speedand pure rolling contact, without slippage, is obtained along the fulllength of the rolls and work piece, resulting in an improved product andlonger roll life.

Since a thread rolling operation results in the generation ofconsiderable heat, it is necessary to provide a supply of coolant to therolls to keep their temperature at a relatively low level. Heretofore,such coolant has been directed indiscriminately over the whole area ofoperation and has had a cooling function only. I improve the operationof my tool by directing coolant through the interior of the tool to thesurface of each roll individually. This concentration of the coolantflow, besides simplifying the piping of the complete machine andproviding the necessary cooling efilect, also eflectively washes thesurfaces of the rolls to remove particles of metal which constantlyadhere thereto, leaving the roll surfaces properly clean and free offoreign matter destructive to the correct thread form on the work piece.

Automatic screw machines of the type to which my device is intended tobe applied often provide a very limited amount of space in which thetool must move laterally from a rest position into operative positionand return. In its rest position, the tool must be withdrawn far enoughto permit the work to be indexed. In prior constructions, theseconsiderations have severely limited the size of the tool andconsequently, the size of the threading rolls, which should be made aslarge as possible to provide a greater amount of rolling surface andthus distribute the wear of the rolling operation over a larger area aswell as provide for stronger supporting members. I have provided novelmechanism for further retracting the most obtrusive portion of the toolwhen it is in rest position and without any additional lateral movementof the shank or holder by which the tool is supported. By this means,the rolls and their supporting members, for any given size of work andmachine, may be made larger than has heretofore been possible, withconsequent increase in the useful life of the rolls and in the strengthof the supporting members.

It is accordingly an object of this invention to provide, in a threadrolling appliance a novel combination of spaced rolls for relativelateral adjusting movement on the work piece and novel compensatingmechanism to correct for taper or parallelism of the work piece and wearwithout sacrificing rigidity of the mechanism or accuracy of the workdone.

Another object is to provide such a thread rolling device having novelmechanism of improved accuracy, rigidity and life for the adjustment ofthe space between the roll axes to effect adjustments in the diametricalsize of the finished work piece.

It is a further object of my invention to provide an improved device forrolling tapered threads from a lateral direction, having rolls whoseaxes are inclined relative to the work axis to achieve equal surfacespeeds of rolls and work piece along the entire line of contacttherebetween.

Another object is to provide an improved device for rolling taperedthreads from a lateral direction, in which the larger ends of the rollsoperate upon the larger end of the Work and the smaller ends of therolls operate upon the smaller end of the work.

A further object is to provide an improved thread rolling appliance inwhich a flushing coolant, is supplied individually to each roll from theinterior of the device in novel manner.

A still further object of my invention is to provide a novel replaceablethrust bearing arrangement for absorbing the axial pressures induced inthe rolls during the rolling operation.

Further objects and advantages of the present invention will be apparentfrom the following description thereof and from the accompanyingdrawings, in which Figure l is a side elevation of a tool embodying myinvention for rolling taperedthreads"and"wnich"is shown at the point oftintsning a rolling operation upon a work tece, p Figure 2' is' aside'elevational view showing the :opposite side of the tool showmFigure-1 with the holder broken away in part,

Figure 3-1s'anend elevationalview of thetool shown in Figure l,

Figure4 is-a vertical-sectional-view taken along-line 4--4 of Figure 2,

Figure 5 is a vertical sectionalview taken substantially along line 'S-Spf Figure 4 Figure 6 is a horizontal sect-tonal VIEW takensubstantially along line 6-6 ofFigure 1,

Figure 7 is a vertical sectional-view taken substantially'alongline7--7*of Figure '6, I

Figure 8 is -a-sid'e' eleVatio'nal-view of the tool similar to Figure 1but'showing the -tool asit appears-whennot in operation,

Figure 9 is a fragmentary sectional view taken substantially along-line9-9-of Figure 3,

Figure 10 is' a fragmentary sectional view taken along line 10-10 ofFigure 9,

Figure 11 is a'fragmentary sectional vtew taken substantially' alongline 11-'-11 ot' Figure-3,

Figure 12 is a-fragmentary' sectional view taken substantially alongline 12-12ot' Figure-2,

Figure 13 is'a' stantially along 'line 13-13 of Figure 1,

Figure 14 is a' fragmentary sectionalvtew taken substantially along line1414 of-Figure-4,

Figure 15 is a side elevational view of a tool embodying my inventionfor rolling straight threads,

Figure 16 tially-along'line 16-16 of Figure 15;

Figure '17 is a-side elevational view of the tool shown in Figure'l5,taken-fromth'e side opposite thereto, and

taken sub- Figure 1 8 -is a horizontalasectional view stantially alongline:18-18 ofi-Figure 15.

Referring to t the drawings, a= preferred embodiment of my improvedthread rolling' tool for rolling threads onta'pered workpiecesis'showntin Figures 1 to 14 inclusive thereof. Thistool comprisesa-holder which is adapted to be s'ecuredto 'a-cam operated tool slide ofan automatic screw'machine '(not shown) for example, which-slide' moves:in a. pathperpendicular to the axis-of the rotatingwork piece. A frame32 is supported by holder 30 in a manner rolls 34, 36. The pitchdiameter of-each roll is approximately; an integer-multiple of the-pitchdiameter of the thread to be rolled. In this illustrative embodimentthis multiple is taken as -4-.- Consequently, each of the rolls 34; 36is provided with a four start thread, the

form of which is-the inverse of the'form of the thread to be produced.

To minimize slippage between therolls and the work piece, therotational' speeds ofrolls andthe work piece must be a constantratio-atallpoints along the length of the thread. Since the rolls aredriven by contact with the workpiece and'since the relative speeds ofrolls and the work piece are inversely proportional to the respectivediameters thereof; a-consta-nt speed ratio at all points along thelengthof the thread is impossible with the prior roll structures. Ieliminate this prior disadvantage by tapering1rolls 34 and 36 suitablywith their smaller diameter ends in contact with the smaller diameterend of the work and with their larger diameter ends in contact withthelarger' end of the work. In the form shown the sine of the angle oftaper of each roll is four times the sine of 'theangle of taper of thework piece. With this combination of diameters and taper and by reasonof the fact that the large and small ends of the rolls 34,- 36- arelocated s'o as to operate respectively on the large and small ends ofthe work piece, the elements of:the' conesof rolls and work piece will,if extended, meet in a common apex. Thus; equal peripheral speeds. of:work piece." and rolls are assured at all points along the 'len'gth ofthe thread. 7

As shown most clearly inz-Figures 4-and 7, rolls 34 and 36 arepositioned in an open space 38in the interior of frame 32 and arerotatablyjournalled' upon a pair of sleeves 40 and 42- r'espect-ively.Sleeves 40 and 42 and rolls 34 and36 are supported by a pair of spindlesis a verticalsectional view taken substanfragmentarysectional-view-taken subto be described later andiniturntrotatablyrsupportsa pair of threading .3:

44 and 46 respectively which pass A" separable" plate-48 (figures 3-and- 4) is secured to one side of frame 32 by means of screws 50. Bothspindles 44 and 46 are similarly mounted, partially in frame 32 andpartially in plate 48. Taking spindle 44 for example, this spindle isprovided near one end thereof with an enlarged diameter portion 52(Figure 4) which has a bearing simultaneously in aligned bores in plate48 and frame 32. The opposite end of spindle 44 is journalled in abushing 54 located in a suitable opening in frame 32. Spindle 44 ismounted with its axis inclined relative to the central horizontal planeof the tool, which plane contains the axis of the work, so that theperiphery. of tapered roll is properly inclined relative to theperiphery of work piece. The angle between axis of work piece and axisof spindle 44 in this case therefore is one-half the included angle oftaper of the work piece plus one-half the included angle of taper of theroll. The spindle 46 is mounted with the same inclination in-theopposite directions At-its end journalled in plate 48, spindle 44 isprovided with a further enlarged head portion 56 which seats withprovision for limited universal movement in a counterbore 58 in plate48. As seen in Figure l, a wrench socket 60 is. formed in the headportion 56 for the manual rotation of spindle 44. Socket 60 is eccentricrelative to head 56 by afew thousandths of an inch. This eccentricity isexaggerated for illustrative purposes in thisfigure. The central portion62 of spindle 44 is formed concentrically with socket 60 and hence alsoeccentricallyrelative to portions 52 and 56. The end portion 64 ofspindle 44 which is journalled in bushing 54 is formed concentricallywith portions 52 and 56 and 'eccentrically relative to central portion62.

Manual rotation of spindle 44, as by means of a wrench inserted insocket 60, will have the effect of through the sleeves.

altering the position of the central portion 62 of spindle 44 relativeto the horizontal central plane of the tool. By such rotationtheperiphery, of roll 34, which is supported by. portion 62, may be movednearer to or farther from the axis of the work. This, together with theidentical mounting of spindle 46 permits precise adustment for the rolls34, 36 to roll the desired size of thread.

As best seen in Figure 13, spindle 44 is provided with a peripheralgroove 66 adjacent to head 56. The inner sloping side of groove 66 isengaged by the head of a screw 68 which is passed through plate 48 andthreadedly engaged in the side of frame 32. Thus screw 68 serves tohold" spindle 44 in correct axial position and, at the same time, tomaintain any previously set rotary adustment of said spindle. Notch 70(Figure l) is formed in the head 56 to permit the insertion and removalof screw 68. Graduations 72 are inscribed on the exterior surface ofhead 56 in order to provide, with a suitable index mark 74 on plate 48,a means of conveniently measuring the rotary adjustment of spindle 44.These details also are duplicated for spindle 46.

The above-mentioned bushing 54 is provided with an enlarged flangeportion 76 (Figure 4) which is seated in a suitable counterbore in frame32. The opening through bushing 54 which receives end portion 64 ofspindle 44 -is formedeccentrically relative to both outer diameters ofthe said bushing (Figure 2). Again, the amount of'this eccentricity isexaggerated on the drawing for illustrative purposes. As a result ofthis eccentricity, rotation of bushing 54 will alter the position of endportion 64 of spindle 44 relative to the axis of the work. Since thisalteration in position affects only one end of spindle 44, rotation ofbushing 54 therefore provides fine adjustment of the inclination ofspindle 44 and therefore'of the taper of the thread to be formed.

Such adjustment must, of necessity, be very small in order to preventthe binding of spindle 44. It will be noted that bearing portion 52 ofsaid spindle is made quite narrow for the same purpose, and is relievedby an adjacent tapered portion. The end portion 64 is likewise beveledas at80, thus keeping the actual bearing surfaces of spindle 44 to aminimum.

A pair of openings 82 (Figure 2) are provided in flange 76 for themanual rotary adjustment of bushing 54 by the use of a suitable spanner.Graduations 840m flange 76 and index marks 86 on frame 32 are providedto measure such adjustment. As seen in Figures 2 and 4, the-outer edgeof flange 76 is beveled for at least for engagement by the head of ascrew 88 threaded into frame 32 adjacent the periphery of flange 76.Thus screw 88 maintains both the axial and the adjusted rotary positionsof bushing 54. The above described taper adjustment is also duplicatedfor spindle 46.

These adjustments of diameter and taper provide distinct advantages notheretofore obtained in a device of this type. They make possible theproduction of threaded parts having precise accuracy as to diametricalsize and taper. Furthermore they provide a means of maintaining suchaccuracy in spite of wear which is normally experienced due to therotation of the rolls. Finally, the wear members, bushings 40 and 42may, when badly worn, be replaced at little expense.

Inwardly adjacent the enlarged bearing portion 52, (Figure 4) sleeve 40is formed with a flange 90 which serves as a thrust bearing for a bevelgear 92 (Figures 4 and 5) which is journalled for rotation upon sleeve40. The inwardly facing end of bevel gear 92 is provided with a pair oflugs 94 which extend therefrom into a pair of openings 96 formed in theadjacent end surface of roll 34. By this means roll 34 and gear 92 areslidably keyed together for unitary rotation. A similar gear 98 isjournalled upon sleeve 42 and is similarly keyed to roll 36. These gears92 and 98 are connected by a series of meshing bevel gears 100, hereshown as three in number (Figure 5). Thus rolls 34 and 36 are connectedfor positive unitary rotation. The pitch cones of gears 92, 98 and 100,rolls 34 and 36 and the work piece all have a common apex. Thus a purerolling movement, without danger of slippage, is assured between rollsand work piece. The small amount of taper adjustment described above,while affecting this theoretical relationship actually need not be largeenough to be considered from this aspect, except that it may benecessary to reduce the tooth thickness of the bevel gears slightly fromthe standard.

Each of the idling bevel gears 100 is similarly mounted. As shown inFigures 5 and 6, gears 100 are positioned in openings 102 in a sidesurface of frame 32. The typical gear 100 (Figure 6) is mounted on aflanged bushing 104 which is in turn journalled on a pin 106. Pin 106 isformed with an integral threaded portion which is threadedly engaged inplate 48 and from which pin 106 extends through bushing 104 into anopening 108 in frame 32. Since it is necessary, at least initially, torotate one roll relative to the other for the purpose of obtaining theproper synchronism between the lateral positions of the threads on therolls, one of the openings 102 is enlarged as at 110 so that one gear100 may be readily removed and replaced.

It is Well known in the art that the tooth-and-gap relationship betweenthe two rolls at the points where they contact the work piece varies asthe work blank W proceeds inwardly between the rolls from the dottedline position in Figure 1 until its axis lies in the plane containingthe axes of the rolls as shown in the full line position, Figure l, atwhich point the operation is completed. Since my rolls are positivelygeared together, no difference between them in rotational speed ispossible. Therefore, the variation in their tooth-and-gap relationshipmust be compensated for by axial movement of the rolls. If both rollsare permitted to move axially during the rolling operation, they tend tomove in opposite directions. ing position, 1, therefore, prevent oneroll from moving axially. This fixed roll will then take the heavierportion of the stress of rolling and will actually roll the thread to aslight degree in an axial direction. The free roll will necessarily berequired to move twice as far axially as it would move if both rollswere free.

In the embodiment shown I have confined roll 34 against axial movement.To avoid excessive wear on the sides of the opening 38 in which therolls rotate, a

replaceable thrust bushing 112 (Figure 4) is provided for roll 34. Thisbushing surrounds the hub of bevel gear 92 and has a flange whichextends between the end face of roll 34 and one side of the opening 38.As shown in Figures 9 and 10, pins 114 are embedded in suitable openingsin the side of opening 38 and extend outwardly therefrom to engagecorresponding notches 116 in the circumference of bushing 112 to keysaid bushing against rotation. A similar thrust bushing 118 (Figure 4),similarly mounted and keyed, is provided for roll 36. The

flange of bushing 118 is made somewhat thinner than the To achieve some,definite startflange of bushing 112 to allow space for the requiredaxial movement of roll 36 during the rolling operation. At the oppositeend of roll 36, a thrust plate 120 is mounted in a suitable counterborein the side of opening 38. Plate 120 surrounds spindle 46 but is inclearance relation thereto. As seen in Figures Hand 14, pins 122,embedded in frame 32, extend therefrom to engage notches 124 in thecircumference of thrust plate 120 to prevent rotation of said plate.Openings 126 are formed in frame 32, adjacent to and co-axial withbushing 130. Compression springs 128 (Figure 12) are positioned inopenings 126 and are held in compression between the flange ot'eccentric bushing 130 and one side of thrust plate 120. Thus thrustplate 120 is resiliently held against the side face of roll 36 and saidroll may move resiliently toward the left (as seen in Figure 4) againstthe pressure of spring 128, the counterbore in which plate 120 ismounted being made deep enough to accommodate such movement.

A similar thrust plate 132, similarly'mounted and keyed is provided forroll 34 with the difference, however, that no springs are provided andsaid plate 132 fits snugly between the end face of roll 34 and frame 32with no provision for axial movement of said roll.

Thrust members 112, 118, 120 and 132 provide an economical means ofmaintaining the original accuracy, since any or all of them may bereplaced after wear at lit.le cost. In prior constructions, in whichsuch replaceable thrust bearings are not provided, it is necessary, ifthe effects of wear are to be removed, to replace the much moreexpensive frame of the tool.

The entire assembly of frame, rolls, gears, etc. described above ismounted for pivotal movement in holder 30, the two arms 134 and 136(Figure 6) of which extend along opposite sides of the assembly.Referring particularly to Figure 6 it will be seen that a pivot pin 138is threadedly engaged in the side of frame 32 and extends outwardlytherefrom through a suitable opening in arm 134. A second pivot pin 140having an enlarged head 142 is passed through arm 136 and is received ina suitable bore in plate 48. Pin 140 is retained in position axially byscrews 144 which pass through head 142 and are engaged in threaded holesin plate 48. Thus since pins 138 and 140 are co-axial, the frameassembly is mounted for limited rocking movement on holder 30 and aboutsaid pins as centers.

In the withdrawal of the toollaterally away from a finished thread it isnecessary for the roll 34 also to move laterally due to the helicaladvance of the thread which is now fully formed on the work piece. Tomake this movement possible, provision is made for the lateral movementof frame 32 and all associated parts, on pins 138 and 140 between thetwo arms of the holder 30. A spring 146 (Figure 6) located in an opening148 in the side of frame 32, and a detent 150 associated therewith holdsthe frame assembly resiliently away from arm 134 and against arm 136.The lateral movement of roll 34 and the withdrawal movement iscommunicated to frame 32 which moves toward arm 134, compressing spring146.

As shown in Figure 7 my improved tool also comprises provision for asupply of coolant to each roll individually. A tube 152 is positionedwithin a vertical bore 154 in frame 32, the ends of which bore aresealed as by plugs 156. An internally threaded opening 158 is provided,leading diagonally into tube 156 from the exterior surface of the frame32. In operation opening 158 is connected to any convenient supply ofcleansing coolant which is fed through tube 152 and the openings 160therein to points adjacent the threading .rolls 34, 36. I have foundthat directing coolant in this manner to each roll, besides providingthe desired cooling effect, serves the very useful purpose of cleansingthe surfaces of the rolls of particles of metal which adhere thereto andcarries such particles into the coolant sump, leaving the roll surfacesproperly clean for the rolling of finely finished threads.

The side of frame 32 which is to be positioned toward the chuck of themachine on which the tool is used, is recessed at 162 to receive arm 134of holder 30 (Figures 2 and 6). By this means arm 134 does not protrudemuch beyond the surface of frame 32 permitting working close to thechuck to avoid bending the work. The limits of the rocking movement offrame 32, described above, are set by the contract between the bev- 7eled" surfaces 164 and 166 with the adjacent surfaces of recess 162. v

To minimize wear on th'e threading rolls and .thereby toincrease theiruseful life, they should be made as large as possible. Size is limitedby conditions under which the tool'is to be used and particularly by thepath of the-work piece as the indexing head of the machine carries saidwork piece'into position to be threaded. In Figure 8, the referencecharacter W indicates the work piece and the broken line 168 representsthe path of a point on the circumference of the work-W as it is movedinto position for the thread rolling operation. Any tool usedon themachine, therefore, must withdraw to the right of line 168 while thework indexes. I have accordingly provideda tension spring 170 which isconnected (Figure 3) at its=opposite ends to pins 172 and 174 which areembedded respectively in plate 48 and arm 136. of holder 30. When thetool is at rest the frame assembly is rocked about the pivots 138 and140 by the tension of spring 170 to the position shown in Figure 8. Thispermits the forward part of the tool to clear the work path.168with'a'minirnum withdrawing movement.

When the tool moves horizontally forward to roll a threadon the workW,.roll 36 comes into contact with the work first and this contact, inthe continued advance of the tool, causes the frame assembly to berocked into an upright position, extending the spring 170. The brokenline 176 in Figure 8 indicates the position which frame 32 would assumein the rearmost position of the tool if spring 170 were not used; It isapparent from the intersection of lines 168 and 176-that with the samewithdrawing movement and without my improved mounting, the tool wouldnotclear the work path and would have to be made smaller, withconsequent loss of worka ing surface on the rolls and with weakerspindles.

The embodiment of my invention as adapted for rolling parallel(non-tapered) threads which is illustrated in Figures to 18 inclusive isgenerally similar to the tool already described with specificdifferences to'be setforth below. Similar parts are designated by thesame reference numerals used for corresponding parts of the tool forrolling threads on'tapered work pieces.

The essential difference in this modification of my invention is thatthe axes of work piece, threading rolls and connecting gears do notconverge to a common point but are disposed parallel to eachother.Instead of bevel gears, spur gears are used. Otherwise, all.theimprovements, adjustments and-advantages of the tapered thread rollingdevice are present here also. ence is the substitution of a single.pivot pin 1 78 for the two pins 138 and 140. This pin 178 -pa'ssescompletely through both arms 134 and 1360f holder 30 and through theframe 32 and plate 48 between them; The axial position of pm 178 ismaintained by the provision of an integral collar 180 thereon,externally of arm 136 of holder 30. Collar 180 is engaged by the head ofa screw- 182,.threadedly engaged in arm 136 and serving simultaneouslyto "holdvpin 178 in correct axial position and to lock it againstrotation. This construction is preferable to the use of two pins wherespace permits.

The invention may be embodied in other specific forms without departingfromthe spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in-all respectsas-illustrative and not restrictive, the scope of 'the'invention beingindicated by the appended claims rather than by theforegoing-description, and all changes whichcome within the meaning andrange of equivalency of the claims are therefore intended to be embracedtherein.

What is claimed and desired to be secured by United States LettersPatent is:

1. An appliance for rolling screw threads by movement laterally onto awork piece comprising a holder for mounting said appliance in a machinetool; a frame-member mounted in said holder; a'pair of spindlesrotatably mounted in said frame member each having two concentric endportions and a central portioneccentricthereto; a firstpair of bushingssurrounding said eccentric central portions of said spindles, eccentricbushings supporting corresponding end portions of said spindlesrotatively mounted in said frame member for independent adjustmentrelative to the respective spindles, the other end portions ofsaid'spindles havingmeansrpermitting One otherdiffermember; a-firstthreading roll mounted on one'of said firstpair of bushings;thrust members for preventing axial-movement of said first threadingroll, a second threading'roll mounted on the other of said first pair ofbushings, a thrust member for limiting axial movement ofsaid secondthreading roll in one direction, a second thrust member,.and meansresiliently urging said second thrust member and said second threadingroll in said one direction.

2. An appliance for rolling screw threads comprising a holder formounting said appliance in a machine tool; a resiliently biased framemember pivotally and slidably mounted in said holder; a pair of spindlesrotatably mounted in said frame member each having two concentric endportions and a central portion eccentric thereto; a first pair ofbushings each surrounding said eccentric central portion of one of saidspindles; a pair of eccentric bushings each supporting one end portionof one of said spindles in said frame member and mounted for rotativeadjustment relative to the spindle to adjust the spindle axes angularlyrelative to each other; means for securing said bushings in adjustedposition relative to the respective spindles and frame member; a firstthreading roll mounted on one of said first pair of bushings,replaceable thrust members surrounding spaced portions of one of saidspindles and having thrust receiving surfaces engageable, respectively,with the opposite ends of said first threading roll and additionalsurfaces engageable with said holder for preventing axial movement ofsaid first threading roll; a second threading roll mountedonthe-other ofsaid first pair of bushings; a re placeable thrust member surroundingthe other of said spindles and having a thrust receiving surfaceengageable with one end of said second threading roll and an additionalsurface engageable with said holder for limiting axial movement of saidsecond threading roll in one direction; a replaceable thrust memberencircling a portion of said other of said spindles and having a radialface engageable with the opposite end of said second threading roll; andresilient means mounted in said holder for urging said last-mentionedreplaceable thrust member and'said second threading roll axially in saidone direction.

3. An appliance for rolling screw threads by movement'laterally onto awork piece comprising a frame structure, ap'air of spindles; bearingportions on each of said spindles for mounting said spindles in saidframe structure for rotational movement; a roll supporting portion oneach of said spindles eccentric to said bearing portionswhereby thedistance between the axes of said rolls may be varied by rotation ofsaid spindles; independent manually actuated frame bearings for one ofsaid spindle bearing portions on each of said spindles, and meansmounting said bearings for eccentric move ment with respect to saidframe to vary the relative inclination of the axes of said rolls.

4. In a thread rolling appliance having a frame and a pair ofperipherally opposed threading rolls adjustable relative to each other;adjusting means for said rolls compris ng individual supporting spindlesfor said rolls each having opposite end portions eccentric to thethreading rollaxis mounted for rotation with respect to said frame forindependent adjustment of the spindles about the axis-of said endportions to variably space the threading rollsfrorn eachother foroperation upon work pieces of different sizes, said eccentric endportions at corresponding ends of the spindles being constructed topermit angular rocking movement of said portions relative to the spindleaxes, and bushings journalling the other eccentric end portions of saidspindles rotatably mounted in the frame in eccentric relation to saidother end portions of the respective spindles for adjustment relatlvethereto to angularly position said spindles and threading'rolls withrespect to each other.

5. A thread rolling, appliance as defined by claim'4, together'with agear train mounted in said frame drivingly connecting the threadingrolls with each other for rotation at equal speeds.

6.- In a thread rolling appliance having a frame and a pair ofperipherally opposed threading rolls adjustable relative to each other;adjusting means for said rolls comprising individual supporting'spindlesfor said rolls each having: opposite end' portions eccentric to thethreadingroll axis, the eccentric portions at corresponduniversalrocking motion thereof relative to-said frame *8'5ting;en'ds ofthespindles being rotatably mounted in said frame, bushings rotatablymounted in said frame, said bushings having eccentric bores forsupporting the other eccentric end portions of said spindles wherebyupon rotation of said bushings the spindles may be angularly positionedwith respect to each other and upon rotation of said spindles the axesof the thread rolls may be variably spaced from each other for operationupon work pieces of different sizes.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 885,068 Moy et al. Apr. 21, 1908 964,272 Kaiserrnan July 12,1910 1,145,661 Bailey July 6, 1915 1,653,709 Johnson Dec. 27, 19271,751,078 Drowns Mar. 18, 1930 2,140,289 Hurtt Dec. 13, 1938 2,182,906Unke Dec. 12, 1939 Number 10 Number Ross, F. E.:

Name Date Gould June 11, 1940 Gould Oct. 22, 1940 Aflieck Aug. 8, 1944Ross Mar. 2, 1948 Sendzimer Aug. 23, 1949 Blain Sept. 26, 1950 FOREIGNPATENTS Country Date Great Britain Dec. 1, 1894 Great Britain Jan. 8,1925 Great Britain Feb. 20, 1941 Great Britain Oct. 18, 1932 OTHERREFERENCES Rolling A Steep Taper Thread, Ameri- 12, Sept. 21, 1916, pp.

